Scalable BGP protection from edge node failure using dynamically assigned labels in data packets

ABSTRACT

In one embodiment, a method comprises detecting, by a provider edge router configured for providing reachability for core network traffic to a prescribed destination address prefix, a backup provider edge router relative to the prescribed destination address prefix; allocating, by the provider edge router, a distinct protected next-hop address for reachability to at least the destination address prefix via the provider edge router; and sending via a core network, by the provider edge router, repair information for the prescribed destination address prefix to ingress provider edge routers and a BGP-free core network router in the core network, the repair information enabling the ingress provider edge routers to insert primary and backup switching labels into each data packet of the core network traffic enabling the BGP-free core network router to reroute the received packet to the backup provider edge router if the provider edge router is unavailable.

TECHNICAL FIELD

The present disclosure generally relates to recovery from failure ofedge routers that utilize border gateway protocol (BGP) for tunnelingdata traffic across a BGP-free core network.

BACKGROUND

This section describes approaches that could be employed, but are notnecessarily approaches that have been previously conceived or employed.Hence, unless explicitly specified otherwise, any approaches describedin this section are not prior art to the claims in this application, andany approaches described in this section are not admitted to be priorart by inclusion in this section.

Wide area networks are composed of edge routers that provide connectionsfor a multi-homed network to a destination network via a core network,also referred to as a backbone network. Since the core network must becomposed of core routers that must be able to perform the fastestpossible switching operations for extremely large amounts of datatraffic, the core routers often are implemented using BGP-free corerouters: unlike edge routers that utilize BGP for tunneling data trafficacross a core network to destination networks, BGP-free core routers donot employ BGP protocol and therefore do not need to learn about themillions of Internet protocol (IP) address prefixes that may be utilizedby the edge routers.

However, if an edge router encounters a failure, there is a need torestore traffic within a guaranteed fifty (50) millisecond interval byretunnelling packets to another edge router that advertised thedestination IP address prefix, without the necessity of BGPreconvergence by the edge routers.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the attached drawings, wherein elements having thesame reference numeral designations represent like elements throughoutand wherein:

FIG. 1 illustrates an example system having an apparatus for sendingrepair information to edge routers via a core network and a BGP-freecore router to enable edge router insertion of primary and backupswitching labels into each data packet for rerouting of data packets bythe BGP-free core router, according to an example embodiment.

FIG. 2 illustrates an example implementation of any one of the routersof FIG. 1, according to an example embodiment.

FIG. 3 summarizes a method of an apparatus sending repair information toenable edge router insertion of primary and backup switching labels intoeach data packet for rerouting by the BGP-free core router, according toan example embodiment.

FIG. 4 illustrates an example method of an apparatus sending repairinformation to enable edge router insertion of primary and backupswitching labels into each data packet for rerouting by the BGP-freecore router, according to an example embodiment.

FIG. 5 illustrates example switching labels inserted into a data packetduring transmission via the core network of FIG. 1, according to anexample embodiment.

FIG. 6 illustrates another example method of an apparatus sending repairinformation to enable edge router insertion of primary and backupswitching labels into each data packet for rerouting by the BGP-freecore router, according to a second example embodiment.

FIG. 7 illustrates another example of switching labels inserted into adata packet during transmission via the core network of FIG. 1,according to the second example embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In one embodiment, a method comprises detecting, by a provider edgerouter configured for providing reachability for core network traffic toa prescribed destination address prefix, a backup provider edge routerrelative to the prescribed destination address prefix; allocating, bythe provider edge router, a distinct protected next-hop address forreachability to at least the destination address prefix via the provideredge router; and sending via a core network, by the provider edgerouter, repair information for the prescribed destination address prefixto at least one ingress provider edge router and a Border GatewayProtocol (BGP) free core network router in the core network, the repairinformation enabling the ingress provider edge router to insert primaryand backup switching labels into each data packet of the core networktraffic enabling the BGP-free core network router to reroute thereceived data packet to the backup provider edge router if the provideredge router is unavailable.

In another embodiment, logic is encoded in one or more non-transitorytangible media for execution by a machine, and when executed is operablefor: detecting, by the machine implemented as a provider edge router andconfigured for providing reachability for core network traffic to aprescribed destination address prefix, a backup provider edge routerrelative to the prescribed destination address prefix; allocating, bythe provider edge router, a distinct protected next-hop address forreachability to at least the destination address prefix via the provideredge router; and sending via a core network, by the provider edgerouter, repair information for the prescribed destination address prefixto at least one ingress provider edge router and a Border GatewayProtocol (BGP)-free core network router in the core network, the repairinformation enabling the ingress provider edge router to insert primaryand backup switching labels into each data packet of the core networktraffic enabling the BGP-free core network router to reroute thereceived data packet to the backup provider edge router if the provideredge router is unavailable.

In another embodiment, an apparatus comprises a network interfacecircuit and a processor circuit. The network interface circuit isconfigured for detecting a backup provider edge router, the apparatusimplemented as a provider edge router configured for providingreachability for core network traffic to a prescribed destinationaddress prefix, the backup provider edge router relative to theprescribed destination address prefix. The processor circuit isconfigured for allocating a distinct protected next-hop address forreachability to at least the destination address prefix via the provideredge router. The processor circuit also is configured for generating,for transmission, via a core network, repair information for theprescribed destination address prefix to at least one ingress provideredge router and a Border Gateway Protocol (BGP)-free core network routerin the core network, the repair information enabling the ingressprovider edge router to insert primary and backup switching labels intoeach data packet of the core network traffic enabling the BGP-free corenetwork router to reroute the received data packet to the backupprovider edge router if the provider edge router is unavailable.

DETAILED DESCRIPTION

Particular embodiments enable a core router in a BGP-free core networkto serve as a repairing core router (rP) providing connectivity betweenprovider edge routers (PEs) that utilize BGP to tunnel traffic acrossthe BGP-free core network.

FIG. 1 is a diagram illustrating an example network 10 having one ormore protected Provider Edge (pPE) routers 12, one or more ingressProvider Edge (iPE) routers 14, one or more repair Provider Edge (rPE)routers 16, and one or more BGP-free core network routers 18 serving asrepair routers (rP), according to an example embodiment. The repairProvider Edge (rPE) routers 16 also are referred to herein as “backupprovider edge routers” to reduce confusion with the repair routers (rP)18. The BGP-free core network router 18 serves as a repairing corerouter that reroutes data traffic to a backup provider edge (rPE) router16 if a protected Provider Edge (pPE) router 12 is unavailable. TheBGP-free core network router 18 is part of a BGP-free core network 22that does not utilize BGP protocol, but serves as a “backbone” networkfor edge routers 12, 14, and 16 that tunnel traffic to each other usingthe core network 22.

The provider edge routers 12, 14, and 16 serve as next-hop routers intoand out of the core network 22 for customer edge (CE) routers 20: eachcustomer edge (CE) router 20 can be positioned at the edge an associatedexternal network 24 having one or more globally-distinct IPv4 and/orIPv6 address prefixes 26. Each external network 24 is a distinctAutonomous System (AS).

Hence, ingress provider edge (iPE) routers 14 can tunnel data trafficvia the core network 22 based on inserting (“pushing”) context-sensitivelabels into each data packet, implemented for example as LabelDistribution Protocol (LDP) labels based on multiprotocol labelswitching (MPLS). The egress provider edge routers 12, 16 can outputcontext-sensitive labels for reaching destination address prefixes 26according to BGP. For example, the repair PE router (rPE) (e.g., PE1,PE2) 16 can allocate a repair label (rL) and (optionally) advertise therepair label (rL) with protected prefixes 26. The protected ProviderEdge (pPE) router 12 can advertise repair information for an identifieddestination (e.g., address prefixes 26) to the ingress Provider Edgerouters (iPE) (e.g., PE11 and/or PE22) 14 and to the repairing corerouter (rP) 18, enabling the ingress Provider Edge routers (iPE) 14 topush both primary labels and repair labels within each data packet toensure reachability to the destination network 24 via the repair PErouter (rPE) 16 in the event that the protected Provider Edge (pPE)router 12 is not available.

Hence, the repairing core router (rP) 18 can provide instantaneousrerouting to the repair PE router (rPE) 16 for a destination addressprefix 26 in response to the repairing core router 18 detecting that theprotected Provider Edge (pPE) router 12 is unavailable, where therepairing core router (rP) 18 can instantaneously reroute a data packetto the repair PE router (e.g., PE1) 16 based on manipulating switchinglabels within the received data packet using the repair informationadvertised by the protected Provider Edge (pPE) router 12. Consequently,the data packet can be rerouted before BGP reconvergence among the edgerouters, without the risk of the rerouted data packet encounteringloops. In one embodiment, the repairing core router (rP) 18 can utilizea context-sensitive vector label (vL) generated by the protectedProvider Edge (pPE) router 12 and stored in the data packet: thecontext-sensitive vector label (vL) enables the repairing core router(rP) 18 to access a locally-accessible table to retrieve a repair labelassociated with the vector label for rerouting the data packet to therepair PE router 16. In another embodiment, the protected Provider Edge(pPE) router 12 can allocate a single protected next hop address (pNH)28 for each Protected-Repair PE Pair (i.e., an identified pairing of theprotected Provider Edge (pPE) router and the repair PE router (rPE)) andadvertise an association between a repair next-hop address (rNH) 30 usedby the repair PE router 16 for reaching the destination address prefix26, and the protected next-hop address (pNH) 28 used by the protected PE(pPE) 12 for reaching the destination address prefix.

Hence, the example embodiments enable a protected Provider Edge (pPE)router 12 to send repair information, associating the protected ProviderEdge (pPE) router 12 with an identified repair PE router (rPE) 16, tothe ingress PE routers 14 and the repair router (rP) 18 in the corenetwork 22, enabling the repair router (rP) 18 to execute instantaneousswitching in the core network 22 to the repair PE router (rPE) 16 basedon a detected unavailability of the protected Provider Edge (pPE) router12.

Hence, the example embodiments ensure that no router needs to copyprefixes from another router, such that only the edge router needs tostore its own label for reaching the next-hop destination network, i.e.,only the protected Provider Edge (pPE) router 12 and the repair PErouter 16 need to store their own labels for reaching the next-hopdestination network 24. Further, the BGP-free core network router 18 isnot required to learn any BGP prefix, nor is the BGP-free core networkrouter 18 required to undergo any complicated provisioning efforts;hence, the size of the forwarding and routing tables in any core router18 is independent of the number of BGP prefixes in use by the edgerouters 12, 14, 16.

Further, the choice of a primary path 32 or a backup path 34 via thecore network is chosen solely by the ingress Provider Edge (iPE) router14 according to its internal policies, and is therefore independent ofthe advertisements by the other routers 12 or 16. Further, the exampleembodiments ensure that the backup path 34 is encoded in each datapacket, enabling the BGP-free core network router (rP) to independentlyreroute the received data packet to the repairing PE router (rPE) if theprotected PE router (pPE) is unavailable. Further, the exampleembodiments can be implemented as an improvement in existing networkswithout disruption, as the repair information and the primary and backupswitching labels described herein can be advertised as “optionalattributes” that can be disregarded by existing routers that cannotimplement the example embodiments; in such cases, edge routers can reacha destination address prefix (e.g., “10.0.0.0/8”) via a conventional BGPnext hop address “1.1.1.1” 36 also advertised by the protected PE router(pPE) 12.

Each of the routers 12, 14, 16, 18, and 20 can be referred to also as“apparatus”. In particular, each router (apparatus) 12, 14, 16, 18 and20 is a physical machine (i.e., a hardware device) configured forimplementing network communications with other physical machines (e.g.,customer edge (CE) routers 20) via the network 10. Hence, each apparatus12, 14, 16, 18, and 20 is a network-enabled machine implementing networkcommunications via the network 10.

FIG. 2 illustrates an example implementation of any one of the routers12, 14, 16, 18, or of FIG. 1, according to an example embodiment. Eachof the routers 12, 14, 16, 18, or 20 can include one or more networkinterface circuits 40, one or more processor circuits 42, and one ormore memory circuits 44.

Any of the disclosed circuits of the routers 12, 14, 16, 18, or 20(including the network interface circuit 40, the processor circuit 42,and the memory circuit 44, and their associated components) can beimplemented in multiple forms. Example implementations of the disclosedcircuits include hardware logic that is implemented in a logic arraysuch as a programmable logic array (PLA), a field programmable gatearray (FPGA), or by mask programming of integrated circuits such as anapplication-specific integrated circuit (ASIC). Any of these circuitsalso can be implemented using a software-based executable resource thatis executed by a corresponding internal processor circuit such as amicroprocessor circuit (not shown) and implemented using one or moreintegrated circuits, where execution of executable code stored in aninternal memory circuit (e.g., within the memory circuit 44) causes theintegrated circuit(s) implementing the processor circuit to storeapplication state variables in processor memory, creating an executableapplication resource (e.g., an application instance) that performs theoperations of the circuit as described herein. Hence, use of the term“circuit” in this specification refers to both a hardware-based circuitimplemented using one or more integrated circuits and that includeslogic for performing the described operations, or a software-basedcircuit that includes a processor circuit (implemented using one or moreintegrated circuits), the processor circuit including a reserved portionof processor memory for storage of application state data andapplication variables that are modified by execution of the executablecode by a processor circuit. The memory circuit 44 can be implemented,for example, using a non-volatile memory such as a programmable readonly memory (PROM) or an EPROM, and/or a volatile memory such as a DRAM,etc.

Further, any reference to “outputting a message” or “outputting apacket” (or the like) can be implemented based on creating themessage/packet in the form of a data structure and storing that datastructure in a tangible memory medium in the disclosed apparatus (e.g.,in a transmit buffer). Any reference to “outputting a message” or“outputting a packet” (or the like) also can include electricallytransmitting (e.g., via wired electric current or wireless electricfield, as appropriate) the message/packet stored in the tangible memorymedium to another network node via a communications medium (e.g., awired or wireless link, as appropriate) (optical transmission also canbe used, as appropriate). Similarly, any reference to “receiving amessage” or “receiving a packet” (or the like) can be implemented basedon the disclosed apparatus detecting the electrical (or optical)transmission of the message/packet on the communications medium, andstoring the detected transmission as a data structure in a tangiblememory medium in the disclosed apparatus (e.g., in a receive buffer).Also note that the memory circuit 44 can be implemented dynamically bythe processor circuit 42, for example based on memory address assignmentand partitioning executed by the processor circuit 42.

FIG. 3 summarizes a method of an apparatus sending repair information toenable edge router insertion of primary and backup switching labels intoeach data packet for rerouting by the BGP-free core router, according toan example embodiment. The operations described herein with respect toany of the Figures can be implemented as executable code stored on acomputer or machine readable non-transitory tangible storage medium(e.g., floppy disk, hard disk, ROM, EEPROM, nonvolatile RAM, CD-ROM,etc.) that are completed based on execution of the code by a processorcircuit implemented using one or more integrated circuits; theoperations described herein also can be implemented as executable logicthat is encoded in one or more non-transitory tangible media forexecution (e.g., programmable logic arrays or devices, fieldprogrammable gate arrays, programmable array logic, application specificintegrated circuits, etc.).

In addition, the operations described with respect to any of the Figurescan be performed in any suitable order, or at least some of theoperations in parallel. Execution of the operations as described hereinis by way of illustration only; as such, the operations do notnecessarily need to be executed by the machine-based hardware componentsas described herein; to the contrary, other machine-based hardwarecomponents can be used to execute the disclosed operations in anyappropriate order, or at least some of the operations in parallel.

FIG. 3 summarizes the operations that enable the BGP-free core networkrouter 18, also referred to as the repairing core router (rP) 18, toreroute a received data packet to a backup provider edge (rPE) router 16via a backup path 34 if the protected Provider Edge (pPE) router 12 isunavailable via the primary path 32.

The edge routers 12, 14, and 16 initially can exchange Internet Protocol(IP) address prefix information for destination address prefixes 26 ofdestination networks 24 according to BGP protocol in operation 50. Asnoted previously, no core router 18 utilizes BGP protocol; hence noaddress prefix information is stored in any core router 18. The edgerouters 12, 14, and 16 in operation 52 also can initially exchange labeldistribution protocol (LDP) labels.

In operation 54 a provider edge router (e.g., PE1) can determine that itis capable of handling repaired traffic for a destination address prefix(e.g., “10.0.0.0/8”) 26, and in response allocate a repair label (rL) asan index into its local label table identifying that the destinationaddress prefix is reachable via a next-hop consumer edge router (e.g.,CE1 20). The provider edge router (e.g., PE1) can advertise itself inoperation 54 as an available repair Provider Edge (rPE) router (i.e.,“backup provider edge router”) 16 based on specifying the repair label(rL) with the protected prefix(es) 26 (e.g., as an optional pathattribute in an LDP message). Hence, a backup provider edge (rPE) router16 is an egress provider edge (PE) router that can reach a protectedprefix (P/m) 26 via an external neighboring router, e.g., a customeredge router 20.

The provider edge router (PE0) can recognize that it has its ownexternal path to the external network (“Network 1”) 24 having theaddress prefix “10.0.0.0/8” 26 via the customer edge router “CE2 ” 20,and can advertise reachability to the address prefix “10.0.0.0/8” 26 viaa BGP next hop address “1.1.1.1” 36.

The provider edge router (PE0) 12 also can detect in operation 56 thatthe next-hop reachable address prefix “10.0.0.0/8” 26 is reachable viaanother Provider Edge router, namely the backup provider edge router(rPE) “PE1” 16. In response detecting the backup provider edge (rPE)router “PE1” 16 providing reachability to the locally-reachabledestination address prefix “10.0.0.0/8” 26, the processor circuit 42 ofthe pPE 12 can allocate in operation 56 at least one protected next hopaddress (pNH) (e.g., pNH=1.1.1.2) 28. In one embodiment, the processorcircuit 42 of the pPE 12 can allocate only one pNH 28 for the entirerouter 12; in another embodiment, the processor circuit 42 can allocatea corresponding pNH 28 for all prefixes 26 protected by the same backupprovider edge (rPE) router 16.

The processor circuit 42 of the pPE 12 can send in operation 58, via thecore network 22, repair information for the prescribed destinationaddress prefix “10.0.0.0/8” 26 to at least one ingress provider edgerouter (e.g., PE 11) 14 and a Border Gateway Protocol (BGP)-free corenetwork router (rP) 18 in the core network 22, described in furtherdetail below. In one embodiment, the BGP-free core network router (rP)18 can be the penultimate hop router for the pPE router 12; in otherembodiments, the rP router 18 can be another router in the core network22. The repair information enables the ingress provider edge routers(e.g., PE11 and/or PE22) 14 to insert (i.e., “push”) primary and backupswitching labels into each data packet of the core network traffic.

The repair information also enables the rP router 18 in operation 60 tochoose the backup path 34 if the primary path 32 is unavailable, basedon the primary and backup switching labels and locally-stored repairinformation, described below. Hence, the repair information enables therP router 18 to interpret the primary and backup switching labels,enabling the BGP-free core network router 18 in operation 60 to reroutethe received data packet to the backup provider edge router (e.g., PE1)16 if the provider edge router PE0 12 is unavailable (e.g., based onpopping and/or swapping the primary and backup switching labels,described below).

FIG. 4 illustrates an example method of the protected Provider Edge(pPE) router 12 sending repair information to enable edge routerinsertion of primary and backup switching labels into each data packetfor rerouting by the BGP-free core router, according to an exampleembodiment. As described below, the processor circuit 42 of theprotected Provider Edge (pPE) router 12 can be configured for generatinga vector label (vL) (82 of FIG. 5) for every backup provider edge (rPE)router 16, and sending repair information to the ingress PE routers 14and the repairing core router (rP) 18 based on the vector label 82.

As described previously, the ingress provider edge routers 14 inoperation 62 can learn about the remote network prefixes 26 via theirBGP peers 12 and 16. For example, the iPE routers “PE11” and “PE12” 14can learn in operation 62 that the destination address prefix“10.0.0.0/8” 26 is reachable via router “PE0” (e.g., via the BGP nexthop address 36) or “PE1”, and that the destination address prefix“20.0.0.0/8” is reachable via router “PE0” or “PE2”.

The BGP-capable routers “PE1” and “PE2” can determine in operation 64that they can serve as backup routers to the router “PE0” for thedestination network prefixes “10.0.0.0/8” 26 and “20.0.0.0/8”,respectively. Hence, the routers “PE1” and “PE2” can configurethemselves as backup provider edge (rPE) routers 16 based on allocatinga repair Next-Hop address (rNH) 30, and advertising the available rNHaddress 30 for the respective destination network prefixes 26. Forexample, the rPE “PE1” 16 can advertise prefix “10.0.0.0/8” 26 isreachable via the repair next hop address “rNH1=9.9.9.1” 30, and the rPE“PE2” can advertise that the prefix “20.0.0.0/8” 26 is reachable via therepair next hop address “rNH2=9.9.9.2” 30.

Each repair PE router (rPE) 16 also can allocate in operation 66 arepair label (rL) (84 in FIG. 5) that can be a 20-bit standard MPLSlabel. The repair label (rL) 84, generated by the rPE 16 for eachcorresponding customer edge router (e.g., CE1) 20, is a pointer into alocal label table entry in the corresponding repair PE router (rPE) thatidentifies the next-hop customer edge router (e.g., “CE1 ”) 20 for theassociated destination address prefix 26. For example, the repair PErouter (rPE) “PE1” 16 can generate a repair label “rL1=3100” that pointsto a table entry in PE1 identifying the next hop router “CE1 ” 20 forthe destination address prefix “10.0.0.0/8” 26; the repair PE router“PE2” also can generate a corresponding repair label (rL) 84 for theaddress prefix “20.0.0.0/8” reachable via the customer edge router “CE4”20. Each repair PE router (rPE) 16 in operation 66 can advertise thegenerated repair label (rL) 84 with the protected prefixes 26 (e.g., PE1advertises “rL=3100” for “10.0.0.0/8”). Although not described in detailherein, similar operations are performed by the rPE router “PE2” 16 withrespect to the prefix “20.0.0.0/8” 26. Note that the repair label (rL)84 and protected prefixes 26 need not necessarily be advertised by therepair PE router (rPE) 16, as other means are possible for providing therepair label-prefix association to the other provider edge routers.

The protected PE (pPE) router 12 in operation 68 can allocate acorresponding vector label (vL) 82 for every repair PE (rPE) router 16(e.g., “vL1=1100” for PE1; “vL2=1200” for PE2), and can configure asingle protected next-hop address (e.g., pNH=1.1.1.2) 36 for the entirerouter “PE0” and that is distinct from the normal BGP next hop address36.

Hence, the protected PE (pPE) router 12 can send repair information thatenables the ingress PEs (iPEs) 14 to insert switching labels. Inparticular, the pPE router 12 in operation 70 can send to the ingress PErouters 14 an advertisement message that associates the vector label(vL) 82 with the repair next-hop address (rNH) 30, for example in theform of a repair next-hop address-vector label (rNH, vL) binding (e.g.,rNH1=9.9.9.1; vL1=1100). The protected PE (pPE) router 12 also can sendto the BGP-free core network router (rP) 18 in operation 72 anadvertisement message that associates the protected next hop address(pNH) 28, the repair next-hop address (rNH) 30, and the vector label(vL) 82 (e.g., pNH=1.1.1.2, rNH1=9.9.9.1, vL1=1100).

The ingress provider edge (iPE) routers 14 and the core router (rP) 18in operation 72 also can learn the appropriate label switched paths forreaching the protected next hop (pNH) address 28 and the repair next hop(rNH) address 30, and add the appropriate entries into their local labeltables. For example, the protected PE (pPE) router 12 can advertise themapping (pNHL1, pNH) that specifies that the label “pNHL1” (86 of FIG.5) is used to reach the protected next hop address “pNH=1.1.1.2” 28; thepPE router 12 also can advertise the mapping (VPNL1, 10.0.0.0/8) thatspecifies a layer 3 service label “VPNL1” (88 of FIG. 5) is used toreach the address prefix “10.0.0.0/8” 26 via the protected PE (pPE)router PE0 12. An example layer 3 service label is a VPN label as usedin Layer 3 Virtual Private Networks (L3VPN), although other types oflayer 3 service labels can be used.

Hence, the ingress PE (iPE) routers 14 can build tables that specifyprimary and backup labels for insertion into each data packet, enablingthe BGP-free core network router to reroute the received data packet tothe repairing PE (rPE) router “PE1” if the protected PE (pPE) router 12is not available. More specifically, each iPE router can chooseaccording to its own policies what path should be used as a primarypath, and what path should be used as a secondary (backup) path.Assuming with respect to FIG. 1 that the iPE router 14 chooses theprotected PE (pPE) router “PE0” as the primary path 32 for reaching thedestination address prefix “10.0.0.0/8” 26 and the router “PE1” as therepair PE (rPE) router 16 for the backup path 34 for reaching thedestination address prefix “10.0.0.0/8” 26, the iPE router can create alocal label table entry specifying that for the destination prefix“10.0.0.0/8” 26, the iPE 14 should push the following labels into anyreceived data packet in the following order, as illustrated for the datapacket 98 in FIG. 5: <VPNL1>88, <rL=3100>84, <vL1=1100>82, and <pNHL1>86(as a transport label for reaching the primary next hop address pNH 28).

The repairing core router (rP) 18 in operation 74 also can add a tableentry into a context-sensitive table for the router PE0 12 specifyingthat: if pPE 12 is reachable, then pop three (3) labels and forward topPE 12 as the next hop; if pPE 12 is not reachable, then pop the labelpNHL1 86, use the vector label “vL1=1100” 82 as an index into thecontext-sensitive table for router PE0 12 to locate a correspondinglabel “rNHL1” (92 in FIG. 5) for reaching the repair PE router “PE1” 16,and swap the vector label 82 with the repair next hop label “rNHL1” 92to forward the data packet (114 of FIG. 5) along the backup path 34 tothe repair PE router (rPE) “PE1” 16. For link-state interior gatewayprotocols (IGPs), “pNH” can be advertised by the repairing core router(rP) 18 with a “maximum metric” so as not to affect the path taken bythe data traffic flowing from the iPEs 14 to the pPE 12.

Although not described in detail herein, similar operations can beexecuted for implementing labels in the iPEs 14 and the rP 18 forestablishing the primary and backup paths for reaching the destinationaddress prefix “20.0.0.0/8”.

FIG. 5 illustrates example switching labels inserted into a data packetduring transmission via the core network of FIG. 1, according to anexample embodiment. Assuming the ingress PE (iPE) router “PE11” receivesa data packet from the customer edge router “CE11” 20 and specifying adestination IP address 90 of “10.1.1.1”, the ingress PE 14 can accessits internal label table as described above and insert (“push”) theprimary and backup switching labels 94 overlying the layer 3 servicelabel “VPNL1” 88 for reaching the destination address prefix“10.0.0.0/8” 26 (operation 96). The ingress PE (iPE) router “PE11” canoutput the packet 98 in operation 100 into the core network 22, causingthe repairing core router (rP) 18 to receive the data packet 98. Therepairing core router (rP) 18 can be implemented as a penultimate hoprouter having a data link connected to the protected PE (pPE) router“PE0” 12; optionally, the repairing core router (rP) 18 can be multiplehops from the protected PE (pPE) router “PE0” 12. If the repairing corerouter (rP) 18 determines the protected PE (pPE) router “PE0” 12 isavailable, the repairing core router (rP) 18 in operation 102 can remove(i.e., “pop”) the top three labels, namely “pNHL1” 86, the vector label(vL) 82, and the repair label (rL) 84. Hence, the repairing core router(rP) 18 in operation 104 can output the modified packet 106 to theprotected PE (pPE) router 12, which can “pop” the layer 3 service label88 and use the layer 3 service label 88 as an index into a local labeltable that specifies the next hop for the incoming label “VPNL1” is thecustomer edge router “CE2 ” 20. Hence, the protected PE (pPE) router“PE0” 12 can output the modified packet 108 in operation 110 to thecustomer edge router “CE2 ” 20 for delivery to the destination network“Network 1” 24.

If the repairing core router (rP) 18 determines the protected PE (pPE)router “PE0” 12 is not available, the repairing core router (rP) 18 inoperation 112 can “pop” the “pNHL1” label 86 and use the vector label(“vL1=1100”) 82 as an index to locate the corresponding repair next hoplabel “rNHL1” 92 associated with the vector label 82 in thecontext-specific label table for the protected PE (pPE) router “PE0” 12.As illustrated in FIG. 5, the repairing core router (rP) 18 can swap thevector label 82 with the repair next hop label “rNHL1” 92 for reachingthe repair next hop address “rNH1=9.9.9.1” 30, and output in operation116 the modified data packet 114 for delivery to the repair next hop(rPE) router 16 via the core network 22.

Assuming the repairing PE router (rPE) “PE1” 16 receives the data packet114 (minus the label “rNHL1” 92 that was popped by its penultimate hoprouter in the core network 22) (i.e., penultimate hop popping), therepairing PE (rPE) router “PEP1” 16 can determine from its repair label(rL) 84 (e.g., “rL1=3100”) that the corresponding table entry in PE1associated with the repair label “rL1=3100” specifies to pop two labels84 and 88, and identifies the next hop router “CE1 ” 20 for thedestination address prefix “10.0.0.0/8” 26. Hence, the repairing PErouter “PE1” 16 can output the modified packet 118 in operation 120 tothe customer edge router “CE1 ” 20 for delivery to the network “Network1” 24.

According to the example embodiment described with respect to FIGS. 1-5,the protected PE (pPE) router 12 allocates a locally unique vector label(vL) 82 per candidate rPE 16. The repairing core router (rP) 18 canstore and “look up” the vector label (vL) 82 within a label contextcorresponding to the pPE 12 (e.g., within a local table designated foronly the pPE 12), enabling the rP 18 to correctly reroute a data packetonto an alternate (backup) path 34 based on a determined unavailabilityof the pPE 12. The ingress PE (iPE) 14 pushes four labels (88, 84, 82,and 86 of FIG. 5) overlying the layer 3 service label 88 and thedestination IP address 90, ensuring that the primary and backupswitching labels 94 are encoded into each data packet. Hence, theprocessor circuit 42 of the repairing core router (rP) 18 can pop threelabels 86, 82, and 84 if the primary PE (pPE) router “PE0” 12 isavailable, and otherwise pop the label 86, and swap the vector label(vL) 82 with the repair next hop label (rNHL1) 92 in response to adetermined absence of the primary PE (pPE) router “PE0” 12. Since therepair label (rL) 84 is allocated by the repairing PE (rPE) router “PE1”16, the repairing PE (rPE) router “PE1” 16 can forward the repairedtraffic correctly by popping two labels 84 and 88, and forwarding themodified packet 118 to the correct customer edge router “CE1 ” 20.

FIGS. 6 and 7 illustrate the processor circuit 42 of a protected PE(pPE) router “PE0” sending repair information to the iPE routers 14 andthe repairing core router (rP) 18 to enable insertion of primary andbackup switching labels into data packets for rerouting by the repairingcore router (rP) 18, according to a second example embodiment.

FIG. 6 illustrates another example method of an apparatus sending repairinformation to enable edge router insertion of primary and backupswitching labels into each data packet for rerouting by the BGP-freecore router, according to a second example embodiment. FIG. 7illustrates another example of switching labels inserted into a datapacket during transmission via the core network of FIG. 1, according tothe second example embodiment.

As described previously with respect to FIG. 4, the edge routers 12, 14,and 16 can learn about the remote network prefixes 26 via their BGPpeers in operation 62, and the backup provider edge routers (rPE) 16 canallocate repair next hop addresses (rNH) 30 on a per customer edgerouter (CE) basis. Hence, the repairing PE (rPE) router “PE1” 16 canallocate the repair next hop address “rNH1=9.9.9.1” 30 for the customeredge router “CE1 ” 20 providing reachability to the destination addressprefix “10.0.0.0/8” 26, and the repairing PE (rPE) router “PE2” 16 canallocate the repair next hop address ““rNH2=9.9.9.2” 30 for the customeredge router “CE4” 20 providing reachability to the destination addressprefix “2.0.0.0/8” 26.

In operation 130 of FIG. 6 the processor circuit 42 of each backupprovider edge router (rPE) 16 can allocate a repair label (rL) 84 on aper customer edge (CE) router basis, create an internal table entryusing the repair label as an index for reaching the destination addressprefix 26 via the corresponding customer edge router 20, and advertisethe repair label (rL) 84 with the particular prefixes. For example, thebackup provider edge router (rPE) “PEP” 16 can advertise the repairlabel “rL1=3100” 84 is associated with the address prefix “10.0.0.0/8”26, and the backup provider edge router (rPE) 16 “PE2” can advertise therepair label “rL2=4100” 84 is associated with the address prefix“20.0.0.0/8” 26.

The protected Provider Edge (pPE) router “PE0” 12 allocates in operation132 a distinct protected next hop address (pNH) 28 for all protectedprefixes 26 that are protected by the same backup provider edge router(rPE) 16. For example, the protected provider edge (pPE) router “PE0” 12can allocate “pNH1=1.1.1.2” 28 for “PE1” 16, and “pNH2=1.1.1.12” 28 for“PE2” 16.

The protected Provider Edge (pPE) router “PE0” 12 in operation 134 sendsan advertisement message to the ingress Provider Edge (iPE) routers 14that associates the protected next hop address 28, the repair next hopaddress 30, and the protected prefix 26, for example “(pNH1=1.1.1.2,rL1=3100, 10.0.0.0/8)” and “(pNH2=1.1.1.12, rL2=4100, 20.0.0.0/8)”.Hence, each ingress Provider Edge (iPE) router 14 can create a tableentry specifying that a prescribed destination address prefix (e.g.,“10.0.0.0/8”) 26 is reachable via a protected next hop address (e.g.,“pNH1=1.1.1.2”) 28 using the associated repair label (e.g., “rL1=3100”).Similar to operation 74 of FIG. 4, each ingress Provider Edge (iPE)router 14 can add the appropriate labels to its label table for pushingthe primary and backup switching labels (140 of FIG. 7) into each datapacket (142 of FIG. 7), including the label “pNHL1” (144 of FIG. 7) forthe protected next hop address “pNH1” allocated by the protected PErouter “PE0” for all prefixes protected by the corresponding repairingPE (rPE) (e.g., “PE1”) 16. As illustrated in FIG. 7, each ingress PE(iPE) can push the primary and backup switching labels 140 overlying thelayer 3 service label 88, where in this second embodiment the primaryand backup switching labels 140 can include the repair label 84 and theprotected next hop label 144 associated with the protected next hopaddress “pNH1” 28. The ingress PE (iPE) router 14 can output the datapacket 142 in operation 146 for delivery to the repairing core router(rP) 18 via the core network 22.

The protected Provider Edge (pPE) router “PE0” 12 in operation 138 sendsa second advertisement to the repairing core router (rP) 18 thatadvertises the association between the protected next hop address (pNH)28 and the repair next hop address (rNH) 30, for example “(pNH1=1.1.1.2,rNH1=9.9.9.1)” for the protected prefix “10.0.0.0/8” 26, and“(pNH2=1.1.1.12, rNH2=9.9.9.2)” for the protected prefix “20.0.0.0” 26.Hence, as illustrated in FIG. 7, the repairing core router (rP) 18 cancreate a local table entry that specifies that if in operation 148 theprotection next hop address (e.g., pNH1=1.1.1.2) 28 is reachable, therepairing core router (rP) 18 can pop the two labels 144 and 84, andoutput the modified data packet 106 in operation 104 for delivery to theprotected PE (pPE) router 12 as described previously with respect toFIG. 5. The repairing core router (rP) 18 also can create a local tableentry based on the advertisement received from the protected PE (pPE)router 12 in operation 138: the local table entry can specify that if inoperation 150 the protected PE (pPE) router 12 is not available, therepairing core router (rP) 18 can swap the top label “pNHL1” (used forreaching the protected next hop address “pNH1” 28) with the label“rNHL1” 92 for reaching the repair next hop “rNH1” address 30. Therepairing core router (rP) 18 can output the modified data packet 114for delivery to the repairing PE (rPE) router “PEP1” 16 as describedpreviously with respect to FIG. 5.

As apparent from the foregoing, the repairing core router (rP) 18 alsocan create a second local table entry that specifies that if theprotected PE (pPE) router 12 is not available to deliver to the customeredge router “CE3” 20 a data packet destined for the network “Network 2”having the destination prefix “20.0.0.0/8” 26, the repairing core router(rP) 18 can swap the label “pNHL2” (used to reach the protected next hop“1.1.1.2”) with a corresponding label “rNHL2” for the repair Next Hop(rNH) address “rNH2=9.9.9.2” 30 for delivery of the data packet to thedestination network “Network 2” 24 via the second repair Next Hop (rNH)router “PE2”.

According to the second example embodiment, the protected PE (pPE)router 12 can allocate a globally distinct protected next hop (pNH)address 28 per protected next hop-repair next hop (pPE-rPE) pair. Hence,since every protected next hop (pNH) address 28 corresponds to adistinct repair next-hop address (rNH) 30, the repairing core router(rP) 18 can reroute traffic to the correct repair Protected Egress (rPE)16 if the protected PE (pPE) router 12 fails.

While the example embodiments in the present disclosure have beendescribed in connection with what is presently considered to be the bestmode for carrying out the subject matter specified in the appendedclaims, it is to be understood that the example embodiments are onlyillustrative, and are not to restrict the subject matter specified inthe appended claims.

What is claimed is:
 1. A method comprising: detecting, by a provideredge router configured for providing reachability for core networktraffic to a prescribed destination address prefix, a backup provideredge router relative to the prescribed destination address prefix;allocating, by the provider edge router, a distinct protected next-hopaddress for reachability to at least the destination address prefix viathe provider edge router; and sending via a core network, by theprovider edge router, repair information for the prescribed destinationaddress prefix to at least one ingress provider edge router and a BorderGateway Protocol (BGP)-free core network router in the core network, therepair information enabling the ingress provider edge router to insertprimary and backup switching labels into each data packet of the corenetwork traffic enabling the BGP-free core network router to reroute thereceived data packet to the backup provider edge router if the provideredge router is unavailable.
 2. The method of claim 1, wherein: theallocating includes allocating the protected next-hop address as asingle next-hop address for all protected address prefixes served by theprovider edge router, the protected address prefixes including thedestination address prefix; the method further comprises allocating avector label for the backup provider edge router; and the sendingincludes sending, as at least a part of the repair information, a firstadvertisement associating together the protected next-hop address, thevector label, and a repair next-hop address used to reach the backupprovider edge router.
 3. The method of claim 2, wherein the firstadvertisement enables at least the BGP-free core network router toassociate the backup provider edge router as an alternative to theprovider edge router in response to detecting the vector label in one ofthe data packets.
 4. The method of claim 2, wherein the sending includessending, as part of the repair information, a second advertisementassociating the vector label with the repair next-hop address to theingress provider edge router.
 5. The method of claim 4, wherein thesecond advertisement enables the ingress provider edge router to insertinto each data packet, as part of the primary and backup switchinglabels overlying a layer 3 service label for reaching the prescribeddestination address prefix, a repair label used by the repairing edgerouter for reaching the prescribed destination address prefix, thevector label, and a label for reaching the protected next-hop address.6. The method of claim 5, wherein: the first advertisement enables theBGP-free core network router to send, to the provider edge router ifavailable, the received data packet as a first modified data packet,based on the BGP-free core network router popping from the received datapacket the label for reaching the protected next-hop address, the vectorlabel, and the repair label and the BGP-free core network routerforwarding the first modified data packet via the core network based onthe layer 3 service label; if the provider edge router is available, themethod further comprising the provider edge router selectivelyreceiving, from the BGP-free core network router, the first modifieddata packet based on the layer 3 service label, outputting the firstmodified data packet as a second modified data packet based on poppingthe layer 3 service label overlying a destination address within theprescribed destination address prefix, and forwarding the secondmodified data packet to a consumer edge router providing reachability tothe prescribed destination address prefix; the first advertisementenables the BGP-free core network router to create a table entryrelative to the protected next-hop address that associates the vectorlabel to the repair next-hop address, enabling the BGP-free core networkrouter to send a third modified data packet if the provider edge routeris not available based on: popping the label for reaching the protectednext-hop address from the received data packet, replacing the vectorlabel in the received data packet with a label for reaching the repairnext hop address, and sending the third modified data packet, containingthe label for reaching the repair next hop address, the repair label,the layer 3 service label, and the destination address, to the backupprovider edge router for delivery to the prescribed destination addressprefix.
 7. The method of claim 1, wherein: the allocating includesallocating the protected next-hop address for all destination addressprefixes, including the prescribed destination address prefix, that areserved by the backup provider edge router; the sending includes sendingto the BGP-free core network router, as at least a part of the repairinformation, a first advertisement associating the protected next-hopaddress with a repair next-hop address used to reach the backup provideredge router; the sending further including sending to the ingressprovider edge router, as part of the repair information, a secondadvertisement associating together the prescribed destination addressprefix, a repair label used by the repairing edge router for reachingthe prescribed destination address prefix, and the protected next-hopaddress.
 8. The method of claim 7, wherein the second advertisementenables the ingress provider edge router to insert into each datapacket, as part of the primary and backup switching labels overlying alayer 3 service label for reaching the prescribed destination addressprefix, the repair label, and a label for reaching the protectednext-hop address.
 9. The method of claim 8, wherein: the firstadvertisement enables the BGP-free core network router to send, to theprovider edge router if available, the received data packet as a firstmodified data packet based on the BGP-free core network router poppingfrom the received data packet the label for reaching the protectednext-hop address and the repair label, and the BGP-free core networkrouter forwarding the first modified data packet via the core networkbased on the layer 3 service label; if the provider edge router isavailable, the method further comprising the provider edge routerselectively receiving, from the BGP-free core network router, the firstmodified data packet based on the layer 3 service label, outputting thefirst modified data packet as a second modified data packet based onpopping the layer 3 service label overlying a destination address withinthe prescribed destination address prefix, and forwarding the secondmodified data packet to a consumer edge router providing reachability tothe prescribed destination address prefix.
 10. The method of claim 8,wherein if the provider edge router is not available, the firstadvertisement enables the BGP-free core network router to create a tableentry that associates the protected next-hop address with the repairnext-hop address, enabling the BGP-free core network router to send afirst modified data packet based on: replacing the label for reachingthe protected next-hop address from the received data packet with alabel for reaching the repair next hop address, and sending the firstmodified data packet, containing the label for reaching the repair nexthop address, the repair label, the layer 3 service label, and thedestination address, to the backup provider edge router for delivery tothe prescribed destination address prefix.
 11. Logic encoded in one ormore non-transitory tangible media for execution by a machine and whenexecuted operable for: detecting, by the machine implemented as aprovider edge router and configured for providing reachability for corenetwork traffic to a prescribed destination address prefix, a backupprovider edge router relative to the prescribed destination addressprefix; allocating, by the provider edge router, a distinct protectednext-hop address for reachability to at least the destination addressprefix via the provider edge router; and sending via a core network, bythe provider edge router, repair information for the prescribeddestination address prefix to at least one ingress provider edge routerand a Border Gateway Protocol (BGP)-free core network router in the corenetwork, the repair information enabling the ingress provider edgerouter to insert primary and backup switching labels into each datapacket of the core network traffic enabling the BGP-free core networkrouter to reroute the received data packet to the backup provider edgerouter if the provider edge router is unavailable.
 12. The logic ofclaim 11, wherein the allocating includes allocating the protectednext-hop address as a single next-hop address for all protected addressprefixes served by the provider edge router, the protected addressprefixes including the destination address prefix; the logic furtheroperable for allocating a vector label for the backup provider edgerouter; and the sending includes sending, as at least a part of therepair information, a first advertisement associating together theprotected next-hop address, the vector label, and a repair next-hopaddress used to reach the backup provider edge router.
 13. The logic ofclaim 12, wherein the first advertisement enables at least the BGP-freecore network router to associate the backup provider edge router as analternative to the provider edge router in response to detecting thevector label in one of the data packets.
 14. The logic of claim 12,wherein the sending includes sending, as part of the repair information,a second advertisement associating the vector label with the repairnext-hop address to the ingress provider edge router.
 15. The logic ofclaim 14, wherein the second advertisement enables the ingress provideredge router to insert into each data packet, as part of the primary andbackup switching labels overlying a layer 3 service label for reachingthe prescribed destination address prefix, a repair label used by therepairing edge router for reaching the prescribed destination addressprefix, the vector label, and a label for reaching the protectednext-hop address.
 16. The logic of claim 15, wherein: the firstadvertisement enables the BGP-free core network router to send, to theprovider edge router if available, the received data packet as a firstmodified data packet, based on the BGP-free core network router poppingfrom the received data packet the label for reaching the protectednext-hop address, the vector label, and the repair label and theBGP-free core network router forwarding the first modified data packetvia the core network based on the layer 3 service label; if the provideredge router is available, the logic further operable for the provideredge router selectively receiving, from the BGP-free core networkrouter, the first modified data packet based on the layer 3 servicelabel, outputting the first modified data packet as a second modifieddata packet based on popping the layer 3 service label overlying adestination address within the prescribed destination address prefix,and forwarding the second modified data packet to a consumer edge routerproviding reachability to the prescribed destination address prefix; thefirst advertisement enables the BGP-free core network router to create atable entry relative to the protected next-hop address that associatesthe vector label to the repair next-hop address, enabling the BGP-freecore network router to send a third modified data packet if the provideredge router is not available based on: popping the label for reachingthe protected next-hop address from the received data packet, replacingthe vector label in the received data packet with a label for reachingthe repair next hop address, and sending the third modified data packet,containing the label for reaching the repair next hop address, therepair label, the layer 3 service label, and the destination address, tothe backup provider edge router for delivery to the prescribeddestination address prefix.
 17. The logic of claim 11, wherein: theallocating includes allocating the protected next-hop address for alldestination address prefixes, including the prescribed destinationaddress prefix, that are served by the backup provider edge router; thesending includes sending to the BGP-free core network router, as atleast a part of the repair information, a first advertisementassociating the protected next-hop address with a repair next-hopaddress used to reach the backup provider edge router; the sendingfurther including sending to the ingress provider edge router, as partof the repair information, a second advertisement associating togetherthe prescribed destination address prefix, a repair label used by therepairing edge router for reaching the prescribed destination addressprefix, and the protected next-hop address.
 18. The logic of claim 17,wherein the second advertisement enables the ingress provider edgerouter to insert into each data packet, as part of the primary andbackup switching labels overlying a layer 3 service label for reachingthe prescribed destination address prefix, the repair label, and a labelfor reaching the protected next-hop address.
 19. The logic of claim 18,wherein if the provider edge router is not available, the firstadvertisement enables the BGP-free core network router to create a tableentry that associates the protected next-hop address with the repairnext-hop address, enabling the BGP-free core network router to send afirst modified data packet based on: replacing the label for reachingthe protected next-hop address from the received data packet with alabel for reaching the repair next hop address, and sending the firstmodified data packet, containing the label for reaching the repair nexthop address, the repair label, the layer 3 service label, and thedestination address, to the backup provider edge router for delivery tothe prescribed destination address prefix.
 20. An apparatus comprising:a network interface circuit configured for detecting a backup provideredge router, the apparatus implemented as a provider edge routerconfigured for providing reachability for core network traffic to aprescribed destination address prefix, the backup provider edge routerrelative to the prescribed destination address prefix; and a processorcircuit configured for allocating a distinct protected next-hop addressfor reachability to at least the destination address prefix via theprovider edge router; the processor circuit configured for generating,for transmission, via a core network, repair information for theprescribed destination address prefix to at least one ingress provideredge router and a Border Gateway Protocol (BGP)-free core network routerin the core network, the repair information enabling the ingressprovider edge router to insert primary and backup switching labels intoeach data packet of the core network traffic enabling the BGP-free corenetwork router to reroute the received data packet to the backupprovider edge router if the provider edge router is unavailable.